A new species of Sigambra (Polychaeta, Pilargidae) from the abyssal plains of the NE Atlantic

4 Pages·2000·1.7 MB·

by  Gordon L J Paterson

Bull. nut. Hist. Mus. Land. (Zool.)66(2):167-170 Issued30November2000
A
new species of Sigambra (Polychaeta,
Pilargidae) from the abyssal plains of the
NE
Atlantic yy £3 3 ° ° ^ %
• *
GORDON LJ PATERSON AND ADRIAN G. GLOVER
PolvchaeteResearch Group, DepartmentofZoology, TheNaturalHisto?yMuseum, London SW75BD, UK.
INTRODUCTION 52701#47 1-3 cm 0.3 mm sieve 1 ind. (LA) 21/5/1991.
ChallengerCruise 111:53201#23 l-3cm0.3mm 1 ind. 13/4/1994;
53201#26 1-3 cm 0.3 mm sieve 1 ind., 1-3 cm 0.5 mm sieve 2
SNDsmpiuoEergrciaeAinmtelgbsaarbnwauatannisdwcaaiwnasnitbtdyeiesnsdssspepainertlvcieeifaepidslse,adtia.unbndseIdyti(ncwoRgeafirscrteatecihcneooeltnrysdbaepeltdin.htcefhu1irod9cou9om4sm)ci,sionntmauamnbduteynnieisnpiwrtgteiedosseanpstfeeorcroioo.femfsTttthhhhoeeeef 553322iinn00dd15..,.##233--20559.3cc1mmm-3m01c.30mm-mm10m.cs2i5me1vmsieinmedi.vneds.1i41e/1vi44en//d14.1,9/i913n49-d;9.54,;c1m-30.c5mm0m.5smiemvesi1eivned.,1
18/4/94.
CapVerdeAbyssalPlaininthesouthtothePorcupineAbyssalPlain
in the north. Tagus Abyssal Plain centred on 38°N 11°W 5035 m: Discovery
Cruise 186: SBC365 3 ind. 26/9/1989; SBC366 1 ind. 26/9/1989;
SBC367 5 ind. 26/9/1989; SBC368 5 ind., SBC369 2 ind. 27/9/
MATERIAL AND METHODS 1989; SBC371 2 ind. 28/9/1989.
W
Madeira Abyssal Plain centred on 31°10' N 21°10 4985m:
Allspecimenswerecollectedusingamodified UnitedStatesNaval DiscoveryCruise 194: 12174#35: 1-3cm0.3 mmsieve2ind.: 1-3
hPEolorericcztuorpnoitnnaielc,lsyMLaiandbteooir0art-ao1raync,dm,sCpa1ap-de3ecVbemorxdaencdoArb3ey-rs5s(aSclBmCP)ll.aayiSenrassmwpaelnredespsrfeorcctoeimsosnteehdde c112m211707.445##45m33::m11s--i33evccemm1 00i..n33d.;mm3mm-5s1icienmvde.02.252i/nmd8./m1293s9/i0e8.v/e19390ind. 21/8/1990.
TctoharrgeourusgaAhnbdayosnnsulamylbtPehlreaiionnfnwseeirernveienstea-kseu1n,bc0wo.ir5tehasnawdvee0rg.ee3mpmartmoic.ceasSlsalemydpmtlohedrsiofufigrehodmab0to.hx3e 1122117744##8600:0—1I-3cmcm0.03.m3mmmsiesvieev1ein1di.n;d5.-2140/8c/m1909.05.mmsieve 1 ind.
mm 28/8/90.
sieve.
CapeVerdeAbyssalPlaincentredon20°N30°W4500-4600m:Dis-
MSpaetceirmieanlsshtauvdeibeeden deposited in a numberoftaxonomic institu- coveryCruise204: 12600#32O-l cm0.3mmsieve 1 ind.6/10/1994.
tions and corresponding registration numbers are given below. Inadditionthefollowingmaterialwasexamined:Sigambrabidentata
Abbreviations: AM -The Australian Museum, Sydney; LA - Los Britaev & Saphronova, 1981 Natural History Museum Polychaete
Angeles County Museum of Natural History; MNHN - Museum Collection Z1986:178-183 (5 paratypes), Vityaz Stn 7488 38°
Nationald'HistoireNaturelle, Paris; BMNH-TheNatural History 41'N:133°45'E 1550m SeaofJapan. SigambragracilisBritaev&
Museum, London: NMNH-National Museum ofNatural History, Saphronova, 1981 ZR1986.184-185(2paratypes),VostokBay,Sea
Smithsonian Institution; NMS - The National Museums of Scot- ofJapan.SigambraphuketensisLicherandWestheide, 1997Z1993.
land; NMW - The National Museum of Wales; ZH Zoologisches 15-16(2 Paratypes), BangTao, W. Phuket Island, Thailand.
Institut und. Museum, Hamburg; ZMUC - Zoological Museum,
Copenhagen.
TAXONOMIC ACCOUNT
Holotype: Porcupine Abyssal Plain Challenger II Criuse 111:
53201#29 48°51.5' N 16°29.6' W, 4844 m, sediment layer 1-3 cm
0.5mmsieve, 14/4/1994 (BMNH 2000. 1852). Family PILARGIDAE
tPraerdatoynpe4s8:°50'PoNrc1u6p°i3n0e'WAbyisns4al85P0lami:n the following samples cen- GenusSIGAMBRA O.F.Muller, 1858
DiscoveryCruise 185: 11908#18: l-3cm0.3 mmsieve 1 ind. 28/8/ Species S. magnuncus sp. nov.
1989. (Figs 1-5)
ChallengerIICruise79: 52701#5: 1-3cm,0.3mm sieve4ind.; 1- Description
3cm0.5mmsieve 2ind(NMSz: 2000.214).16/5/1991. Holotype: Length 3.7 mm for 33 chaetigers, greatest width of
52701#9: 1-3 cm0.5mm 1 ind(ZMH). 17/5/1991. body 0.3 mm.
52701#25: 1-3 cm0.3mm sieve 1 ind.(MNHN-POLY53); 0-1 cm Paratypes: Range from length 0.5 mm for 13 chaetigers to 10.5
0.5mmsieve 1 ind(NMW.Z: 2000.070).; 3-5cm0.5mmsieve2 mm for 50 chaetigers, number of segments depends on size of
ind(NMNH 186794). 20/5/1991; individual. (Fig. 5).
52701#29: 1-3cm0.3 mmsieve 1 ind. (AM); 1 ind. (ZMUC-POL- Body unpigmented; slightly flattened anteriorly, but becoming
1013 21/5/1991. moreroundedposteriorly; anteriorchaetigers widest.
©TheNaturalHistoryMuseum,2000
168 G.L.J. PATERSONAND A.G. GLOVER
Fig.2 SEMsofSigambramagnuncus(MAPDiscoveryInvestigations
12174#800.5mmsieve, 1-3cm)Dorsalviewofanteriorregion.
laterals in smaller specimens, but more level with them in larger
individuals. Apairofcushionlikenuchalorgans, situatedoneither
side ofthe median antennae. Eyes absent. Pharynx withoutjaws,
armed witheightequal size, slightlypointedpapillae.
Peristomiumapproximatelytwiceaslongasfirstchaetiger. Two
pairsoflongtaperingtentacularcirri,dorsalcirrilongerthanventral,
and slightly shorter than median antennae. A row oflow cushion-
like papillae (sense organs) extending across dorsal surface of
peristomium (may onlybe visibleunderhigh magnification).
Fig.1 SEMsofSigambramagnuncus(MAPDiscoveryInvestigations
12174#600.5mmsieve, 1-3cm)A.Generalviewofindividual.B.View
ofnotopodia,notethesmallcapillarychaetaineachnotopodium
Prostomium rounded, slightly indented laterally at insertion of
palps and prostomium. Palps biarticulate with relatively long
palpostyles;palpophoresfuseddistallyoverhalftheirlength.Three Fig.3 a Parapodiumfrommidregion,anteriorview, b notopodial
antennae, median antenna longest, situated slightly posterior to hook,c&dneurocapillaries. Scalebars=0.1 mm.
ANEWN.E. ATLANTICPOLYCHAETE 169
65 otherchaetigersthinandtapering,equaltoorshorterthanneuro-
60 podia, equal to or slightly longer than dorsal cirri. Neurochaetae
simple capillaries, slightly expanded at the base just free of the
55 podia, tipsquickly taperintoaprolongedpoint (Fig. 3 c,d).
50 Pygidium with two taperingcirri. Anus dorsal.
CO
a> 45 Distribution. S. magnuncushasbeenrecordedfromtheabyssal
o> 40 plains ofthe NEAtlantic atdepths from4000m to5085 m.
£
o 35 Etymology. The name of this species derives from the large
o + PAP/53201 conspicuoushookson thenotopodia(Latinmagnus-largeuncus-
zd 30 o+ o PAP hook).
25 TAP
EOS
20
MAP
DISCUSSION
15 • PAP/53205
—
10 -i 1 1 I 1 r- Taxonomic Affinities
4 6 8 10 12
Total Length(mm) Licher& Westheide (1994) suggested that the Pilargidae was nota
separate family and that species in the family belonged in the
Fig.4 Graphshowingtherelationshipbetweensizeandnumberof Hesionidae.ThishypothesishasbeenrejectedbyPleijel(1998)and
chaetigers. Individualsfromdifferentsamplesitesareidentified.PAP- Pleijel and Dahlgren (1998)on the basisthat Licher&Westheide's
PorcupineAbyssalPlain,MAP-MadeiraAbyssal Plain.TAP-Tagus (1994) original study was not rooted in an appropriate outgroup.
Abyssal Plain,EOS-CapVerdeAbyssal Plain. Subsequent analysis by Pleijel and Dahlgren (1998) indicated that
the Pilargidae and Hesionidae were different and non-overlapping
Parapodia biramous; anterior parapodia laterally orientated, be- groups. We. therefore, retain the family Pilargidae.
coming more dorsal in median and posterior chaetigers. A row of Including S. magnuncus, there are 17 described species of
cushion-like papillae extending across dorsal surface between Sigambra (Licherand Westheide, 1997). Basedon examination of
notopodiaon each chaetiger. Sigambra material in the NHM and the revision of Licher &
Notopodiapointed, with straight, blunt-tipped internal aciculae. Westheide (1997), S. magnuncus shares certain features with S.
Dorsal cirri ofchaetiger 1 long, thin and tapering; nearly equal in ocellata (Hartmann-Schroder, 1959), S. bidentata Britaev &
length to median antenna; subsequent dorsal cirri initially shorter Saphronova. 1981 and S. qingdaoensis Licher& Westheide, 1997,
withwiderbases,butinposteriorchaetigersbecomingmoreslender namely the ventral cirrus is missing on chaetiger 2 and there are
longerandprojectingdorsally.Largehooksemergentonchaetiger3 eight papillae in the pharynx (Licher & Westheide, 1997). The
(Fig. lb, 2, 3b) until one or two chaetigers from pygidium; in relative proportions ofthedorsal and ventral cirri suggest similari-
posteriorchaetigershooksmeetinginmidline. Short,delicatecapil- tieswithS.ocellata,however,inS.magnuncusthenotopodialhooks
lariesprojectingfrommostnotopodia,justoneinanteriorchaetigers start on chaetiger 3 rather than chaetiger 6 as in S. ocellata. In
(Fig. lb, 3a), usually becoming two in posteriorsegments. 5. bidentataandS.qingdaoensisthenotopodialhookscanstartfrom
Neuropodial lobes pointed, with blunt-tipped, straight aciculae chaetigers3, similartoS. magnuncus,butinadditiontodifferences
(Fig 3a); initiallyorientated laterally butbecome more vertical and incirrallength,S.magnuncusdiffersfrom5.bidentatainnothaving
dorsalinposteriorchaetigers.Ventralcirriabsentonchaetiger2;on bidentateneurochaetae. S. magnuncusdiffersfromS. qingdaoensis
inhavingonecapillarynotochaetainanteriorchaetigers,becoming
12 two in posterior chaetigers. whereas in S. qingdaoensis there are
always two notopodial capillaries. Finally, the notopodial hooksin
10 S. magnuncusaremuch largerthan incomparablesizedindividuals
ofthe otherspecies.
u> 8 Growth and abundance
g
'> S.magnuncuswasmostcommoninsamplesfromthePorcupineand
6c 6 Tagus abyssal plains with densities of4 to 32 individuals per m2
,
o while lower numbers were found in the Madeira and Cap Verde
O 4 samples.Thiswaspartlyduetoloweroveralldensitiesofpolychaetes
at these latter sites (Paterson et at. 1998), but their distribution
suggeststhatthisspeciesismorecommoninnorthernabyssalareas.
Also analysis ofthe distribution within the sediment suggests that
thisspeciesisfoundwithinthe sedimentratherthanonthesurface.
There is a good range of sizes within the collection, allowing
allometricchangestobe noted. Notopodial hooks in smallerspeci-
4 6 8 10 12 mens appear to be extremely large, but in larger specimens these
Total Length (mm) hooks are proportionately smaller. This suggests that hooks are
produced at a set size, not affected by growth. The hooks always
Fig.5 HistogramshowingtherangeofsizesofS.magnuncuscollectedin occurfirstonchaetiger3.
theNEAtlantic. Size of specimens ranges from 0.5 to 10.5 mm, although most
170 G.L.J. PATERSONANDA.G. GLOVER
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supportedbyacontractfromEUMarineScienceandTechnologyprogramme Hermundura tricuspis Muller, 1858 from Brazil and designation of neotypes
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